RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. P10-104949 filed Apr. 15, 1998 which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The present invention relates to a solid-state imaging element having a concave lens structure (interlayer lens) formed therein.
2. Description of the Related Art
In accordance with an increasing demand of miniaturizing an element, recent color solid-state imaging elements come to have a so-called on-chip lens structure in which a microlens is formed on the upper portion of the element and are able to improve sensitivity in a sensor (light-receiving portion) by focusing an incident light with this microlens.
Some solid-state imaging element having the above-mentioned on-chip lens structure further includes a second lens structure having a light condenser characteristic, i.e. interlayer lens formed between the microlens on the surface and the light-receiving portion.
As this interlayer lens structure, there are enumerated a concave lens structure in which a boundary surface between two layers having different refractive indexes is formed as a concave surface on which a concave lens is formed.
In a CCD (charge-coupled device) solid-state imaging element in which the interlayer lens mentioned above is formed, although the interlayer lens should preferably be shaped such that sensitivity may become maximum, lights having various incident angles become incident on the CCD solid-state imaging element depending upon a value of stop (F number) of a camera lens system.
When the F number is large, for example, the incident light is narrowed so that it becomes approximately a vertical light. At that time, a quantity of the incident light decreases.
When on the other hand the F number is small, the incident light is widened so that an oblique light component increases. At that time, a quantity of incident light increases.
However, when a light becomes incident on the curved surface of the interlayer lens from the oblique direction, depending upon its incident angle, the light is totally reflected on the concave surface of the interlayer lens and cannot reach the light-receiving portion. There is then the risk that an improvement of sensitivity becomes insufficient.
Also, with respect to the on-chip lens of the same shape, when the F number of the camera changes, a quantity of oblique light component changes so that sensitivity becomes different.
Therefore, in order to obtain the standards for determining a shape in which sensitivity may become maximum, trial products of interlayer lens have heretofore been manufactured and trial and error have been made.
Then, the optimum shape of interlayer lens capable of avoiding the aforementioned problems and which can sufficiently improve sensitivity has not been yet clarified up to now.